The invention includes method for monitoring and/or limiting the use of a data communications connection subject to payment between IP clients in a packet-switched connection network, in which method the operator terminal, such as a SIP system, of the signalling channel of the connection station of the client is set to control a traffic limiter, such as a firewall in the operator's traffic-relaying system between the source terminal and the destination terminal. The invention also includes a system for limiting the use of a data communications connection subject to payment, between IP clients, in a packet-switched connection network and a computer software product for limiting the use of a data communications connection subject to payment, between IP clients, in a packet-switched connection network.